The Changes of Ergonomic Engine Vibroacoustic Response Regarding Their Development

The article presents the results of research on the vibroacoustic response of internal combustion engines mounted in a vehicle. The vehicles studied belong to popular models, which became available in successive versions. Each group included vehicles of the same model of an older generation (equipped with a naturally aspirated engine) and of a newer generation, including downsized (and turbocharged) engines. Tests in each group were carried out under repeatable conditions on a chassis-load dynamometer. The vibrations were measured using single-axis accelerometers mounted on the steering wheel, engine, and driver’s head restraint mounting. The primary purpose of the study was to verify whether the new generations of vehicles equipped with additional high-speed elements (compressors) generate additional harmonics (especially those within the range potentially affecting travel comfort and human health) and whether there are significant changes in the distribution of spectral power density in the new generations. As the study showed, new generations of vehicles are characterized by a different vibroacoustic response, and the trend of change is the same in each of the families studied.

Transient Vibroacoustic Analysis of Functionally Graded Plates

This paper presents the vibroacoustic response of pure functionally graded plates under transient loading of mechanical nature. The functionally graded plate is modelled using the conventional first-order shear deformation theory to incorporate the effects of transverse shear and rotary inertia. The mid-surface variables are determined using the finite element method. Transient structural response is determined using Newmark Beta time marching scheme and the acoustic pressure in the free field is obtained using the time-domain Rayleigh integral. The effective material properties of the FG plate and the transient response of both the structural and acoustic fields have been computed in MATLAB. The influence of the volume fraction index, thickness ratio and boundary conditions of pure FG plate on its transient vibroacoustic response is investigated by a detailed parametric study.

Method of vibration power spectral density calculation for spacecraft attached large-size and small-mass equipment units

During the lift-off and the ascent phase, spacecraft (SC) large-size attached equipment is impacted by intensive vibrations, largely due to acoustic pressures. To ensure a reliable in-orbit operation of all SC systems the modes of vibration loads shall be assessed as much as reliable (using experimentally-confirmed mathematical models). Determination of the vibroacoustic response parameters of the equipment structure is a very important issue for such equipment units (elements) which have a large surface square with a relatively small mass. Among such structures are folded solar arrays (SA) and reflector type antennae dishes (ART). The purpose of this study is to validate the calculation methodology of vibration power spectral density (PSD) for low and medium frequency band (25-400 Hz), and apply it for the aforesaid structures in the lift-off and flight phases as part of the integrated launch vehicle in the area of maximum ram effects, when the acoustic pressure levels, and therefore their impact on the vibroacoustic response of these structures are maximum. The target goal has been implemented using the example of the solar array and reflector type antenna being used in the spacecraft power supply system and onboard radio system of one of RSC Energia-developed spacecraft. Key words: environment air, spacecraft, solar array, reflector type antennae dish, dynamic model, sound pressure level, acoustic pressure, structure vibroacoustic response.